Magnetic recording medium and magnetic recording and reproducing device using a magnetic recording layer formed with a predetermined concavo-convex pattern

ABSTRACT

A magnetic recording medium including at least a disk substrate  1 A, a magnetic recording layer  5  formed with a predetermined concavo-convex pattern on the disk substrate  1 A, and a non-magnetic layer  6  filled into concave portions of the concavo-convex pattern, so as to have data track regions  20  and servo pattern regions  21 . Due to the existence of concaves and convexes in the surface of each servo pattern region  21 , the foregoing problem is solved. On this occasion, arithmetical mean deviation of the assessed profile Ra of the surface of each servo pattern region  21  is preferably not lower than 0.3 nm. The difference in surface level between each concave and each convex existing in the surface of the servo pattern region  21  is preferably not larger than 6 nm.

BACKGROUND OF THE INVENTION

The present invention relates to a magnetic recording medium andmagnetic recording-reproducing device, and particularly relates to amagnetic recording medium in which stiction between the magneticrecording medium and a head slider flying on the surface of the magneticrecording medium and mounted with a magnetic head for recording andreproducing information into/from the magnetic recording medium isprevented effectively so that crush or the like due to the stiction canbe prevented, and magnetic recording-reproducing device having themagnetic recording medium.

Magnetic recording media such as hard disks have been conspicuouslyimproved in areal density by improved techniques such as finergranulation of magnetic particles for forming magnetic recording layers,alteration of materials, and finer head processing. Further improvementin areal density will be expected in the future. However, the improvedtechniques adopted till now have elicited problems as to side fringes,crosstalk, etc. due to a limit of head processing and a spread of amagnetic field. Thus, the improvement in areal density using thebackground-art techniques has reached its limit.

As one of solutions to the problems, that is, as one of techniques whichcan improve the areal density of magnetic recording media, there havebeen proposed discrete track type magnetic recording media (for example,see JP-A-9-97419 or JP-A-2000-195042). A typical discrete track typemagnetic recording medium has a magnetic recording layer formed withconcentric track patterns, and a non-magnetic layer filled into concaveportions between adjacent ones of the magnetic recording layer patternsso as to extend continuously in the track direction and separate theconcentric track patterns from each other.

In magnetic recording-reproducing device having such a discrete tracktype magnetic recording medium, servo pattern regions serving asreference of tracking control for controlling a magnetic head to trackon a desired track are formed all over the 360° circumference of themagnetic recording medium and, for example, at fixed angular intervalsbetween adjacent ones of data track regions.

FIG. 2 is a schematic configuration diagram showing an example of aservo pattern region formed in a discrete track type magnetic recordingmedium. Servo pattern regions 21 are formed all over the 360°circumference of the magnetic recording medium and at fixed angularintervals between data track regions 20 and 20 adjacent to each other.Each servo pattern region 21 is chiefly constituted by a sync signalregion (preamble region) 22, an address region 23 and a servo burstsignal region 24. The sync signal region 22 serves to fix the reproducedwaveform amplitude by means of an AGC circuit or to securesynchronization with a clock. The address region 23 includes a timingsignal indicating the start position of a sector and serving as areference position of each data track region 20, and an indexidentification signal. The servo burst signal region 24 serves togenerate a position signal indicating a position in a track.Incidentally, the address region 23 includes a track numberidentification function for identifying the number of a track arrangedin the radial direction of the disk and a sector number identificationfunction for identifying the number of a servo pattern arranged in thecircumferential direction of the disk.

The servo burst signal region 24 is a two-phase servo system typicallyconstituted by four burst signal regions 24A, 24B, 24C and 24D.Amplitude differences between burst signals are calculated based on thepair of the first and second burst signal regions 24A and 24B and thepair of the third and fourth burst signal regions 24C and 24D. Thus, ofthe amplitude differences, portions high in linearity are connected toobtain a linear position error signal. Such servo pattern regions 21serve as reference for the magnetic head to accurately trace tracksformed in the magnetic recording medium. Thus, high positioning accuracyis required for forming the servo pattern regions 21.

In manufacturing of a discrete track type magnetic recording mediumhaving servo pattern regions and data track regions, a non-magneticmaterial is filled into concave portions of a predeterminedconcavo-convex pattern with which a magnetic recording layer is formed.Thus, the surface is made flat enough to suppress fluctuation in flyingof a head slider mounted with a magnetic head. As a method of chargingthus, a film formation technique such as sputtering to be used in thefield of semiconductor manufacturing is used. However, when the filmformation technique is used, the non-magnetic material is formed notonly in the aforementioned concave portions but also on the uppersurface of the magnetic recording layer. Thus, irregularities in highrelief caused by the non-magnetic material formed as a layer on themagnetic recording layer are formed in the surface of the magneticrecording medium. Due to the irregularities in high relief, there occurproblems as follows. That is, the flying height of the head slidermounted with the magnetic head and flying due to an air flow on thesurface of the magnetic recording medium rotating at the time ofrecording-reproducing is made unstable, or the gap length between themagnetic head and the magnetic recording layer is increased (that is,the spacing loss between the magnetic head and the magnetic recordinglayer). Thus, the sensitivity is lowered or foreign matters areaccumulated easily.

As a solution to the aforementioned problems, it is desired to flattenthe surface of the magnetic recording layer while removing thenon-magnetic material formed as a layer on the magnetic recording layer.A processing technique such as CMP (Chemical Mechanical Polishing), forexample, used in the field of semiconductor manufacturing is used assuch a flattening method. Typically a texture is formed in the surfaceof a magnetic recording medium so that stiction between the head sliderand the magnetic recording medium is prevented by the effect of thetexture. When the aforementioned CMP method or the like is used to makethe surface of the magnetic recording medium too flat, the effect of thetexture is not exerted sufficiency. Thus, there is a problem that thehead slider is stuck onto the magnetic recording medium so that themagnetic head is crushed easily.

Particularly, with increase in areal density, the flying height of thehead slider may be not higher than 10 nm. In such a case, the headslider and the magnetic recording medium are brought into intermittentcontact with each other. In this state, when the surface of the magneticrecording medium is too flat, there is a problem that friction betweenthe head slider and the magnetic recording medium increases so that themagnetic head is crushed easily for the same reason as mentioned above.

JP-A-2000-195042 proposes a solution to such a problem, in which atexture is formed in the flattened surface of a non-magnetic material,and stiction between a head slider and a magnetic recording medium isprevented by irregularities of the texture so as to prevent crush fromoccurring.

Although the magnetic recording medium disclosed in JP-A-2000-195042 hassome effect in preventing the stiction of the head slider, it isnecessary to add a step of forming a texture in the flattened surface ofthe non-magnetic material. Thus, there is a problem that the number ofsteps in the manufacturing process increases so as to increase the cost.In addition, in the magnetic recording medium manufactured thus, theflattened non-magnetic material remains on the surface of the magneticrecording layer. Thus, there is a problem that the gap length(synonymous with “spacing loss”: the same thing will be applied below)between the magnetic recording layer formed in the magnetic recordingmedium and the magnetic head is increased.

SUMMARY OF THE INVENTION

The present invention was developed to solve the foregoing problems. Itis a first object of the invention to provide a magnetic recordingmedium having a structure which has an effect of preventing stiction ofa head slider, and which is preferably low in spacing loss and superiorin cost merit. It is a second object of the invention to providemagnetic recording-reproducing device having the magnetic recordingmedium.

In order to attain the foregoing first object, a magnetic recordingmedium according to the invention at least includes a disk substrate, amagnetic recording layer formed with a predetermined concavo-convexpattern on the disk substrate, and a non-magnetic layer filled intoconcave portions of the concavo-convex pattern, wherein the magneticrecording medium has data track regions and servo pattern regions. Themagnetic recording medium is characterized in that concaves and convexesexist in a surface of each of the servo pattern regions.

According to the invention, in a hard disk drive or the like providedwith the magnetic recording medium having the concaves and convexes inthe surface of each servo pattern region forming the magnetic recordingmedium, the effect of preventing stiction of a head slider flying on themagnetic recording medium and reading/writing magnetic recordinginformation can be improved due to the existence of the concaves andconvexes. As a result, the hard disk drive or the like can be drivenstably.

The magnetic recording medium according to the invention may be alsocharacterized in that arithmetical mean deviation of the assessedprofile of a surface of each of the servo pattern regions is not lowerthan 0.3 nm.

According to the invention, in a hard disk drive or the like providedwith the magnetic recording medium not lower than 0.3 nm in arithmeticalmean deviation of the assessed profile of a surface of each of the servopattern regions, the surface of the magnetic recording medium isprevented from being too flat due to the arithmetical mean deviation ofthe assessed profile of the surface. Thus, increase in frictionresistance between the magnetic recording medium and a head slider canbe suppressed. As a result, it is possible to prevent stiction betweenthe magnetic recording medium and the head slider flying on the magneticrecording medium and mounted with a magnetic head for reading/writingmagnetic recording information.

The magnetic recording medium according to the invention may be alsocharacterized in that a difference in surface level between each of theconcaves and each of the convexes existing in a surface of each of theservo pattern regions is not higher than 6 nm.

According to the invention, due to the difference in surface levelbetween each concave and each convex existing in a surface of each ofthe servo pattern regions, which difference is not higher than 6 nm, theeffect of preventing stiction can be improved without lowering theflying stability of the head slider flying on the magnetic recordingmedium.

The magnetic recording medium according to the invention may be alsocharacterized in that the concaves and convexes existing in a surface ofeach of the servo pattern regions are formed by a difference in surfacelevel between the magnetic recording layer and the non-magnetic layer,and a thickness-direction surface position of the magnetic recordinglayer is higher than a thickness-direction surface position of thenon-magnetic layer in each of the servo pattern regions.

According to the invention, the concaves and convexes existing in asurface of each of the servo pattern regions are formed by thedifference in surface level between the magnetic recording layer and thenon-magnetic layer, and the thickness-direction surface position of themagnetic recording layer is higher than a thickness-direction surfaceposition of the non-magnetic layer in each servo pattern region.Accordingly, the distance between the magnetic recording layer and themagnetic head can be narrowed to reduce the spacing loss between theboth.

The magnetic recording medium according to the invention may be alsocharacterized in that the thickness-direction surface position of thenon-magnetic layer is not higher than the thickness-direction surfaceposition of the magnetic recording layer.

According to the invention, the thickness-direction surface position ofthe non-magnetic layer is not higher than the thickness-directionsurface position of the magnetic recording layer in each data trackregion and each servo pattern region. Accordingly, the magneticrecording layer is exposed sufficiently. As a result, the distancebetween the magnetic recording layer and the magnetic head can benarrowed to reduce the spacing loss between the both.

The magnetic recording medium according to the invention may be alsocharacterized in that arithmetical mean deviation of the assessedprofile of a surface of each of the data track regions is lower thanarithmetical mean deviation of the assessed profile of a surface of eachof the servo pattern regions.

According to the invention, due to the arithmetical mean deviation ofthe assessed profile of a surface of each of the data track regionslower than the arithmetical mean deviation of the assessed profile of asurface of each of the servo pattern regions, the S/N ratio ofreproduced data in each data track region can be more improved.

The magnetic recording medium according to the invention may be alsocharacterized in that the magnetic recording layer is absent from theconcave portions of the concavo-convex pattern.

According to the invention, due to the absence of the magnetic recordinglayer in the concave portions of the concavo-convex pattern, the problemof noise generated from the concave portions can be eliminated.

The magnetic recording medium according to the invention may be alsocharacterized in that a non-magnetic material for forming thenon-magnetic layer is comprised of one or more compounds selected fromoxides, nitrides and carbides.

According to the invention, the non-magnetic material for forming thenon-magnetic layer is comprised of one or more compounds selected fromoxides, nitrides and carbides. Accordingly, those compounds areexcellent in chemical stability in themselves and difficult to allowcorrosion or the like to occur, for example, due to contact with themagnetic recording layer having a metal component. As a result, it ispossible to provide a magnetic recording medium excellent in chemicalstability.

The magnetic recording medium according to the invention may be alsocharacterized in that a non-magnetic material for forming thenon-magnetic layer is a material having an amorphous structure or amicrocrystalline material.

Normally, the concave portions to be filled with the non-magnetic layerare formed by etching the magnetic recording layer. The groove flanks ofthe concave portions are considerably damaged by the etching so thatdefects such as grain boundaries are produced. Such defects cannot beprotected perfectly by a normal crystalline material having grainboundaries. According to the invention, such defects can be protected byuse of a non-magnetic material which is a material having an amorphousstructure or a microcrystalline material as a filling material.Incidentally, the microcrystalline material means a material having nocrystalline peak in X-ray diffraction.

The magnetic recording medium according to the invention may be alsocharacterized in that a non-magnetic material for forming thenon-magnetic layer has silicon dioxide as a main component thereof.

According to the invention, due to use of a non-magnetic material havingsilicon dioxide as its main component, which material is easy to beetched, good flatness can be obtained particularly in each data trackregion. In addition, it is possible to form a non-magnetic layersuperior in adhesion to the magnetic recording layer and suppressed incrystal grain growth.

In order to attain the second object, magnetic recording-reproducingdevice according to the invention is characterized by including amagnetic recording medium according to the invention, a head sliderdesigned to at least partially fly on a surface of the magneticrecording medium at the time of recording-reproducing, and a magnetichead mounted on the head slider and for recording-reproducinginformation into/from the magnetic recording medium.

According to the invention, the magnetic recording-reproducing device isprovided with the magnetic recording medium having a structure which hasan effect of preventing stiction of the head slider and which is low inspacing loss and superior in cost merit. Accordingly, the head sliderflying on the magnetic recording medium configured thus can fly stablywithout producing crush due to the stiction on the magnetic recordingmedium. As a result, it is possible to provide magneticrecording-reproducing device which can be driven stably.

The magnetic recording-reproducing device according to the invention maybe also characterized in that circumferentially continuous length ofeach of the data track regions in the magnetic recording medium is notlonger than circumferential length of the head slider.

According to the invention, due to the circumferentially continuouslength of each data track region in the magnetic recording medium notlonger than the circumferential length of the head slider, at least apart of head slider is always present in a servo pattern region havingthe concaves and convexes. As a result, stiction of the head slider canbe prevented more surely.

Incidentally, in the specification, “a magnetic recording layer formedwith a predetermined concavo-convex pattern on a disk substrate” impliesnot only a magnetic recording layer divided into a large number ofrecording elements with a predetermined pattern on a disk substrate, butalso a magnetic recording layer partially divided but partiallyconnected, a magnetic recording layer such as a spiral magneticrecording layer formed continuously in a part of a substrate, and acontinuous magnetic recording layer having a concavo-convex pattern inwhich both convex portions and concave portions are formed. Further, inthe specification, “convex portions of a concavo-convex pattern” meansprotruding portions of a concavo-convex shape in a section perpendicularto the surface.

As described above, according to the magnetic recording medium of theinvention, the surface of the magnetic recording medium is preventedfrom being too flat, so that increase in frictional resistance betweenthe magnetic recording medium and a head slider can be suppressed.Accordingly, it is possible to prevent stiction between the magneticrecording medium according to the invention and the head slider flyingon the magnetic recording medium and mounted with a magnetic head forreading/writing magnetic recording information. Thus, problems such ascrush of the magnetic head due to the stiction can be suppressedconspicuously. In addition, it is not necessary to add a step of givinga texture to the surface of the magnetic recording medium. Thus, thecost can be reduced. In addition, the distance between the magneticrecording layer formed in the magnetic recording medium and the magnetichead is so small that the spacing loss can be reduced. Further, it isnot necessary to give a texture to each data track region. Thus, theirregularities in the data track region can be suppressed to be so smallthat the S/N ratio of reproduced data in the data track region can beimproved.

In addition, the magnetic recording-reproducing device of the inventionis provided with the aforementioned magnetic recording medium.Accordingly, it is possible to prevent stiction between the magneticrecording medium and the head slider flying on the magnetic recordingmedium and mounted with a magnetic head for reading/writing magneticrecording information. Thus, it is possible to provide magneticrecording-reproducing device which can conspicuously suppress problemssuch as crush of the magnetic head due to the stiction, and which is lowin spacing loss between the magnetic head and the magnetic recordinglayer, and excellent in cost merit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are schematic sectional views showing layer configurationsof magnetic recording media according to the invention;

FIG. 2 is a schematic plan view of each data track region and each servopattern region in a magnetic recording medium according to theinvention;

FIGS. 3A-3B are schematic sectional views showing an embodiment of themagnetic recording medium according to the invention;

FIGS. 4A-4B are schematic sectional views showing another embodiment ofthe magnetic recording medium according to the invention;

FIGS. 5A-5B are schematic sectional views showing another embodiment ofthe magnetic recording medium according to the invention;

FIGS. 6A-6H are sectional views for explaining a manufacturing processof the magnetic recording medium according to the invention;

FIGS. 7A-7C are sectional views for explaining the manufacturing processof the magnetic recording medium according to the invention;

FIG. 8 is a perspective view showing an embodiment of magneticrecording-reproducing device according to the invention;

FIG. 9 is a schematic plan view showing the area ratio of each convexportion to each concave portion in each servo burst signal region;

FIG. 10 is a graph showing the relationship between the arithmeticalmean deviation of the assessed profile and the frictional coefficient inthe surface of the magnetic recording medium; and

FIG. 11 is a schematic view for explaining the range of a convex portionof a concavo-convex pattern.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed description will be made below about a magnetic recordingmedium according to the invention and magnetic recording-reproducingdevice having the magnetic recording medium.

(Magnetic Recording Medium)

Magnetic recording media according to the invention include hard disks,floppy (registered trademark) disks, magnetic tapes, etc. using onlymagnetism for recording and reading information. However, the magneticrecording media according to the invention are not limited to thosemedia, but also include magneto-optical recording media such as MO(Magnet Optical) disks using both magnetism and light, and thermallyassisted recording media using both magnetism and heat. For example, themagnetic recording media can be represented by a magnetic recordingmedium (see FIG. 2 which will be described later) in which servo patternregions serving as reference of tracking control for controlling arecording-reproducing head such as a magnetic head to track on a desiredtrack are formed all over the 360° circumference of the magneticrecording medium at fixed angular intervals between data track regions.

FIGS. 1A and 1B are sectional configuration diagrams showing an exampleof a fundamental sectional mode of a magnetic recording medium accordingto the invention.

The magnetic recording medium according to the invention shown in FIGS.1A and 1B is a perpendicular recording type magnetic recording mediumhaving a soft magnetic layer. The magnetic recording medium includes atleast a disk substrate 1, a magnetic recording layer 5 formed with apredetermined concavo-convex pattern on the disk substrate 1, and anon-magnetic layer 6 filled into concave portions of the concavo-convexpattern. More specifically, for example, an undercoat layer 2, a softmagnetic layer 3 and an orientation layer 4 are laminated onto the disksubstrate 1 in turn. Further on the orientation layer 4, a magneticrecording layer 5 is formed with a predetermined concavo-convex pattern,and a non-magnetic layer 6 is filled into concave portions of theconcavo-convex pattern. Further a protective film 7 and a lubricatingfilm 8 are formed to cover the magnetic recording layer 5 and thenon-magnetic layer 6.

Incidentally, in FIGS. 1A and 1B, the reference numeral 1A represents adisk substrate which expediently designates a total laminate of theundercoat layer 2, the soft magnetic layer 3 and the orientation layer 4laminated onto the disk substrate 1 successively. FIG. 1A shows asectional mode of a magnetic recording medium 10 in which there is nomagnetic recording layer between elements of a magnetic recording layer5 formed with a predetermined concavo-convex pattern on the disksubstrate 1A. FIG. 1B shows a sectional mode of a magnetic recordingmedium 11 (referred to as “palm type”) in which concaves and convexesare formed in the disk substrate 1A, and a magnetic recording layer 5 isformed thereon as a film following the concaves and convexes. Thefollowing description will be made chiefly based on FIG. 1A about theperpendicular recording type magnetic recording medium 10 having thesoft magnetic layer 3. However, the magnetic recording medium accordingto the invention may be a longitudinal recording type magnetic recordingmedium, or may be a magnetic recording medium 11 in which a magneticrecording layer is present in concave portions of a concavo-convexpattern as shown in FIG. 1B.

First, description will be made about each layer constituting themagnetic recording medium according to the invention.

The disk substrate 1 must be extremely smooth and have no undulation orthe like. Thus, a head slider flying on the magnetic recording mediumformed finally can fly in low height. A glass substrate, an NiP-platedAl—Mg alloy substrate or the like is preferably used as the disksubstrate 1. The thickness of the disk substrate 1 to be used is, forexample, about 300-700 μm. Particularly, the glass substrate is lower insurface roughness than the NiP-plated Al—Mg alloy substrate. Thus, theglass substrate can gain high surface smoothness. In addition, the glasssubstrate is also superior in shock resistance. Therefore, the glasssubstrate is preferably used in a small-size magnetic recording medium.

The undercoat layer 2 is provided for controlling the orientation of thesoft magnetic layer 3 formed thereon, and so on. The soft magnetic layer3 is provided for forming a magnetic circuit between a magnetic head andthe magnetic recording medium, and so on. The orientation layer 4 isprovided for controlling the orientation of the magnetic recording layer5 formed thereon, and so on.

The magnetic recording layer 5 is provided with a predetermined patternas a magnetic recording layer in a hard disk drive or the like. Forexample, in a discrete track type magnetic recording medium, in eachdata track region constituting the magnetic recording medium, a magneticrecording layer is formed so that elements thereof are arranged at verysmall intervals in the radial direction of tracks by a concentricpattern in order to record/reproduce magnetic recording information. Onthe other hand, in each servo pattern region, the magnetic recordinglayer is formed as a pattern to be used as reference of tracking controlfor making the magnetic head track on a desired data track. In addition,for example, in a discrete bit type magnetic recording medium, in eachdata track region constituting the magnetic recording medium, a magneticrecording layer is formed so that elements thereof are arranged at verysmall intervals in the circumferential direction and the radialdirection of tracks by a dot pattern. On the other hand, in each servopattern region constituting the magnetic recording medium, the magneticrecording layer is formed with a pattern corresponding to predeterminedservo information or the like. Preferred examples of materials forforming the magnetic recording layer 5 include Co—Cr-based polygeneticalloys such as CoCrTa, CoCrPt, CoCrPtTa, etc. The magnetic recordinglayer 5 is formed to be 5-30 nm in thickness, 5-1,000 nm in convex widthand 10-2,000 nm in pattern pitch by a film formation method such as asputtering method, and an etching method.

The non-magnetic layer 6 is a layer filled into each concave portion ofthe concavo-convex pattern formed on the disk substrate. Examples ofnon-magnetic materials for forming the non-magnetic layer 6 include SiO₂(silicon dioxide), In (indium), ITO (tin-doped indium oxide), Al₂O₃,TiN, TaSi alloys, Ta, MgO, SiC, TiC, etc. The non-magnetic layer 6 isformed to be, for example, 5-30 nm thick by a film formation method suchas a sputtering method.

According to the invention, it is preferable to select, from theaforementioned various non-magnetic materials, one or more compounds ofoxides (SiO₂, ITO, Al₂O₃, MgO, etc.), nitrides (TiN etc.) and carbides(SiC, TiC, etc.). These compounds are excellent in chemical stability inthemselves and difficult to allow corrosion or the like to occur, forexample, due to contact with the magnetic recording layer 5 having ametal component. Thus, the compounds can provide magnetic recordingmedia excellent in chemical stability. According to the invention,particularly a non-magnetic material having SiO₂ as its primarycomponent is preferably used. SiO₂ is processed by etching so easilythat good flatness can be obtained particularly in each data trackregion by etching. In addition, SiO₂ is superior in adhesion to themagnetic recording layer 5 and also has an effect that it can form thenon-magnetic layer 6 suppressed in crystal grain growth.

Alternatively, non-magnetic materials which are materials having anamorphous structure or microcrystalline materials may be used preferablyas the non-magnetic layer 6. Typically the concave portions to be filledwith the non-magnetic layer 6 are formed by etching the magneticrecording layer 5. The groove flanks of the concave portions areconsiderably damaged by the etching so that defects such as grainboundaries are produced. Such defects cannot be protected perfectly by anormal crystalline material having grain boundaries. Therefore, thedefects such as grain boundaries damaged by the etching can be protectedby use of a material having an amorphous structure with no grainboundaries or a microcrystalline material having grain boundariessubstantially counting for nothing, as the material to be filled.Specific examples of non-magnetic materials having an amorphousstructure include C, Si, SiO₂, Al₂O₃, TaSi alloys, TbFeCo alloys, CoZralloys, etc. The non-magnetic layer 6 is formed to be, for example, 5-30nm thick by a film formation method such as a sputtering method.Incidentally, the microcrystalline materials designate materials havingno crystalline peak in X-ray diffraction.

The protective layer 7 is provided for protecting the surface of themagnetic recording medium so as to secure the sliding durability thereofin cooperation with the lubricating layer 8 which will be describedlater. Particularly, the protective layer 7 is provided for preventingthe magnetic recording medium from being damaged at the time of contactwith the head slider. Examples of materials for forming the protectivelayer 7 include a hard carbon film called diamond-like carbon(hereinafter referred to as “DLC”), zirconium oxide (ZrO₂), silicondioxide (SiO₂), etc. The protective layer 7 is formed to be 1-5 nm thickby a film formation method such as a CVD (Chemical Vapor Deposition)method or a sputtering method. Incidentally, the DLC is an amorphousstructure film having carbon as its primary component, and it is acarbonaceous material showing hardness of about 200-8,000 kgf/mm² byVickers hardness measurement.

The lubricating layer 8 is provided for protecting the surface of themagnetic recording medium so as to secure the sliding durability thereofin cooperation with the aforementioned protective layer 7. Preferredexamples of materials for forming the lubricating layer 8 include liquidfluorine-based compounds such as perfluoropolyether (PFPE). Thelubricating layer 8 is formed to be 1-2 nm thick by a film formingmethod such as a dipping method.

FIG. 2 is a schematic configuration diagram showing an example of datatrack regions and servo pattern regions formed in a magnetic recordingmedium according to the invention. FIGS. 3A-3B, 4A-4B and 5A-5B areschematic sectional views showing examples of magnetic recording mediaaccording to first to third embodiments. Incidentally, in FIG. 2, thehatched portions designate concave portions of a concavo-convex pattern,and the other portions designate convex portions of the concavo-convexpattern. FIGS. 3A-5A are sectional views taken on line A-A in FIG. 2,showing a data track region. FIGS. 3B-5B are sectional views taken online B-B in FIG. 2, showing a servo pattern region. In FIGS. 3A-3B,4A-4B and 5A-5B, in order to elicit the features of the invention, alaminate comprised of a disk substrate 1, an undercoat layer 2, a softmagnetic layer 3 and an orientation layer 4 is designated by a “disksubstrate 1A”, and a protective layer 7 and a lubricating layer 8provided on the magnetic recording layer 5 and the non-magnetic layer 6are not illustrated.

As shown in FIG. 2, a magnetic recording medium according to theinvention includes data track regions 20 and servo pattern regions 21.In each data track region 20, a magnetic recording layer forrecording-reproducing magnetic recording information is formed like atrack. Each servo pattern region 21 serves as reference of trackingcontrol for making a magnetic head track on a desired data track.

The servo pattern regions 21 are formed all over the 360° circumferenceof the magnetic recording medium at fixed angular intervals between thedata track regions 20 and 20. Each servo pattern region 21 is chieflyconstituted by a sync signal region (preamble region) 22, an addressregion 23 and a servo burst signal region 24. The sync signal region 22serves to fix the reproduced waveform amplitude by means of an AGCcircuit or to secure synchronization with a clock. The address region 23includes a timing signal indicating the start position of a sector andserving as a reference position of a data track region 20, and an indexidentification signal. The servo burst signal region 24 serves togenerate a position signal indicating a position in a track.Incidentally, the address region 23 includes a track numberidentification function for identifying the number of a track arrangedin the radial direction of the disk and a sector number identificationfunction for identifying the number of a servo pattern arranged in thecircumferential direction of the disk.

The servo burst signal region 24 is a two-phase servo system typicallyconstituted by four burst signal regions 24A, 24B, 24C and 24D.Amplitude differences between burst signals are calculated based on thepair of the first and second burst signal regions 24A and 24B and thepair of the third and fourth burst signal regions 24C and 24D. Thus, ofthe amplitude differences, portions high in linearity are connected toobtain a linear position error signal. Such servo pattern regions 21serve as reference for the magnetic head to accurately trace tracksformed in the magnetic recording medium. Thus, high positioning accuracyis required for forming the servo pattern regions 21.

In the magnetic recording medium 10 according to the invention is firstcharacterized in that there are concaves and convexes in the surface ofeach servo pattern region 21 as shown in FIGS. 3B, 4B and 5B. Due to theexistence of the concaves and convexes in the surface of each servopattern region 21, the effect of preventing stiction of a head sliderflying on the magnetic recording medium and reading/writing magneticrecording information can be improved in a hard disk drive or the likeprovided with the magnetic recording medium having the concaves andconvexes. As a result, the hard disk drive or the like can be drivenstably.

The concaves and convexes existing in the surface of each servo patternregion 21 are formed by a difference in surface level between themagnetic recording layer 5 and the non-magnetic layer 6 as shown inFIGS. 3B, 4B and 5B. Of these embodiments, as shown in FIGS. 3B and 4B,it is preferable that the thickness-direction position of the surface ofthe magnetic recording layer 5 is higher than the thickness-directionposition of the surface of the non-magnetic layer 6 in each servopattern region 21. In magnetic recording media according to theembodiments, the distance between the magnetic recording layer and amagnetic head can be narrowed so that the spacing loss between the bothcan be reduced. As shown in FIG. 5B, the thickness-direction position ofthe surface of the non-magnetic layer 6 may be made higher than thethickness-direction position of the surface of the magnetic layer 5 ineach servo pattern region 21. In this case, the magnetic recordingmedium can be designed to improve at least the effect of preventingstiction of the head slider.

It is desired that the concaves and convexes existing in the surface ofeach servo pattern region 21 have a difference in surface level notlarger than 6 nm. Within this range, the effect of preventing thestiction can be improved without lowering the flying stability of thehead slider flying on the magnetic recording medium. On the other hand,when the concaves and convexes have a difference in surface level largerthan 6 nm, the flying stability of the head slider may deteriorate tocause a practical problem. Further, from the point of view of thereproduced signal quality of servo information, the difference insurface level is preferably not larger than 3 nm, and more preferablynot larger than 1 nm. Incidentally, the difference in surface level wasmeasured by an atomic force microscope.

Particularly in the magnetic recording medium according to theinvention, the embodiment as shown in FIGS. 3A-3B is preferred. That is,the non-magnetic layer 6 is absent from the surface of the magneticrecording layer 5 in each data track region 20, and the magneticrecording layer 5 in each servo pattern region 21 forms convex portionsof a concavo-convex pattern. According to this embodiment configuredthus, the non-magnetic layer 6 is not formed to cover the surface of themagnetic recording layer 5 in either the data track region 20 or theservo pattern region 21. That is, the thickness-direction surfaceposition of the non-magnetic layer 6 is not higher than thethickness-direction surface position of the magnetic recording layer 5,and the non-magnetic layer 6 is chiefly present in the concave portionsof the concavo-convex pattern. Thus, the magnetic recording layer 5 isexposed sufficiently. As a result, the distance between the magneticrecording layer and the magnetic head can be reduced so that the spacingloss between the both can be reduced.

In the magnetic recording medium according to the embodiment shown inFIGS. 4A-4B, the non-magnetic layer 6 is formed on the magneticrecording layer 5 in each data track region 20. Accordingly, it islikely that there occurs a problem of the spacing loss due to thenon-magnetic layer 6. However, when the non-magnetic layer 6 formed onthe magnetic recording layer 5 is not thicker than 1 nm, the spacingloss becomes small not to result in any practical problem.

On the other hand, when convex portions in each servo pattern region 21are formed by the non-magnetic layer 6 as in the magnetic recordingmedium shown in FIGS. 5A-5B, there is an effect in terms of preventionof stiction of the head slider. However, the non-magnetic layer 6 isformed to be higher (thicker) in thickness-direction surface positionthan the magnetic recording layer 5. Thus, there occurs a spacing lossbetween the magnetic head and the magnetic recording layer in accordancewith the distance by which the non-magnetic layer 6 is formed to behigher (thicker) than the magnetic recording layer 5. As a result, thegap length between the head slider flying on the magnetic recordingmedium and the magnetic recording layer formed on the magnetic recordingmedium increases so that the sensitivity may deteriorate. Incidentally,when the difference in surface level between the magnetic recordinglayer 5 and the non-magnetic layer 6 is not larger than 1 nm in themagnetic recording medium according to the embodiment shown in FIGS.5A-5B in the same manner as described above, the spacing loss becomessmall not to result in any practical problem.

In addition, in the magnetic recording media according to theembodiments shown in FIGS. 3A-3B, 4A-4B and 5A-5B, the magneticrecording layer 5 is absent from the concave portions of theconcavo-convex pattern. Accordingly, there is an effect that the problemof noise generated from the concave portions can be eliminated.

Incidentally, in this specification, the “convex portions of theconcavo-convex pattern” means protruding portions of a concavo-convexshape in a section perpendicular to the surface. Further, assume thateach convex portion 92 of the concavo-convex pattern in thisspecification includes a tapered portion when a tapered angle as shownin FIG. 11 is present in the convex portion 92.

The magnetic recording medium according to the invention is secondlycharacterized in that arithmetical mean deviation of the assessedprofile Ra of the surface of each servo pattern region 21 is not lowerthan 0.3 nm, and preferably not lower than 0.5 nm. In a hard disk driveor the like provided with the magnetic recording medium having such anarithmetical mean deviation of the assessed profile of the surface, thesurface of the magnetic recording medium is not too flat, so that it ispossible to suppress increase in frictional resistance between themagnetic recording medium and a head slider. As a result, it is possibleto prevent stiction between the magnetic recording medium and the headslider flying thereon for reading/writing magnetic recordinginformation, so that there hardly occurs a problem such as crush of amagnetic head due to the stiction. Incidentally, the arithmetical meandeviation of the assessed profile Ra is defined as JIS-B0601-2001.

Here, the arithmetical mean deviation of the assessed profile of thesurface of each servo pattern region 21 means arithmetical meandeviation of the assessed profile of the surface including concaves andconvexes (for example, difference in surface level between the magneticrecording layer 5 and the non-magnetic layer 6) existing in the surfaceof the servo pattern region 21 as shown in FIGS. 3A-3B, 4A-4B and 5A-5Bby way of example. Due to the arithmetical mean deviation of theassessed profile of the surface not lower than 0.3 nm, stiction betweenthe magnetic recording medium and the head slider is prevented so thatcrush of the magnetic head caused by the stiction can be eliminated. Ifthe arithmetical mean deviation of the assessed profile of the surfaceis lower than 0.3 nm, the surface of each servo pattern region 21 willbe so flat that the frictional resistance between the magnetic recordingmedium and the head slider increases. As a result, stiction between themagnetic recording medium and the head slider will occur easily.

On the other hand, according to the invention, concaves and convexes asin each servo pattern region 21 are absent from each data track region20. Accordingly, the arithmetical mean deviation of the assessed profileof the surface of the data track region 20 is lower than thearithmetical mean deviation of the assessed profile of the surface ofthe servo pattern region 21. Thus, there is an effect that the S/N ratioof reproduced data in the data track region 20 can be improved more. Interms of the S/N ratio, the arithmetical mean deviation of the assessedprofile Ra of the surface of the data track region 20 is preferably nothigher than 1 nm and more preferably not higher than 0.5 nm. If thearithmetical mean deviation of the assessed profile Ra of the surface ofthe data track region 20 is higher than 1 nm, the S/N ratio may bereduced to increase servo tracking errors. Incidentally, the method ofmeasuring the arithmetical mean deviation of the assessed profile of thesurface in the data track region 20 is similar to the aforementionedmethod in the servo pattern region 21.

According to the magnetic recording medium of the invention, asdescribed above, the surface of the magnetic recording medium is not tooflat, so that increase in frictional resistance between the magneticrecording medium and the head slider can be suppressed. Accordingly, itis possible to prevent stiction between the magnetic recording mediumaccording to the invention and the head slider flying on the magneticrecording medium and mounted with a magnetic head for reading/writingmagnetic recording information. Thus, a problem such as crush of themagnetic head caused by the stiction can be suppressed conspicuously.Further, it is not necessary to provide a step of giving a texture tothe surface of the magnetic recording medium. Thus, the cost can bereduced. In addition, the spacing loss can be reduced due to a smalldistance between the magnetic recording layer formed in the magneticrecording medium and the magnetic head. Moreover, it is not necessary togive a texture to any data track region. Thus, irregularities in theservo pattern region can be suppressed to be so small that the S/N ratioof reproduced data in the data track region can be improved.

In the magnetic recording medium according to the aforementionedembodiment of the invention, the undercoat layer 2, the soft magneticlayer 3 and the orientation layer 4 are formed under the magneticrecording layer 5. The invention is not limited to such a configuration.The configuration of layers under the magnetic recording layer 5 can bechanged suitably in accordance with the kind of magnetic recordingmedium. For example, one or two layers of the undercoat layer 2, thesoft magnetic layer 3 and the orientation layer 4 may be omitted, or themagnetic recording layer 5 may be formed directly on a substrate.

In the aforementioned embodiment, the magnetic recording medium 10according to the invention is a perpendicular recording discrete tracktype magnetic disk in which the magnetic recording layer 5 is divided atminute intervals in the radial direction of tracks. However, theinvention is not limited to such a configuration. Not to say, theinvention is also applicable to a magnetic disk in which a magneticrecording layer is divided at minute intervals in the circumferentialdirection (sector direction) of tracks, a magnetic disk in which amagnetic recording layer is divided at minute intervals in both theradial direction and the circumferential direction of tracks, a palmtype magnetic disk having a magnetic recording layer with a continuousconcavo-convex pattern as shown in FIG. 1B, and a magnetic disk having aspiral magnetic recording layer.

(Method for Manufacturing Magnetic Recording Medium)

Next, description will be made about an example of a method formanufacturing the aforementioned magnetic recording medium. FIGS. 6A-6Hand 7A-7C are sectional views for explaining a manufacturing process ofthe magnetic recording medium according to the invention. Incidentally,the following manufacturing method is merely an example. Manufacturingthe magnetic recording medium is not limited to the following method.

First, a disk substrate 1 is prepared, and an undercoat layer 2, a softmagnetic layer 3, an orientation layer 4 and a magnetic recording layer5 are formed and laminated with predetermined thicknesses on the disksubstrate 1 in that order, for example, by a sputtering method or thelike (see FIG. 6A). A first mask layer 61 and a second mask layer 62 areformed and laminated on the magnetic recording layer 5 in that order,for example, by a sputtering method or the like, and a resist layer 63is further laminated thereon, for example, by a dipping method or a spincoat method (see FIG. 6B). Here, for example, the first mask layer 61 isformed out of TiN or the like, the second mask layer 62 is formed out ofNi or the like, and the resist layer 63 is formed out of negative typeresist (such as brand name NBE22A made by Sumitomo Chemical Co., Ltd.).

Next, a predetermined concavo-convex pattern is transferred to theresist layer 63 by a nano-imprint method so as to form a resist pattern.After that, the resist layer at the bottom of each concave portion ofthe resist pattern is removed by reactive ion etching using O₂ gas asreactive gas (see FIG. 6C). Alternatively, the resist pattern may beformed by a photolithographic method.

Next, the second mask layer 62 exposed from the bottom of each concaveportion of the resist pattern is removed, for example, by ion beametching using Ar (argon) gas. For example, the second mask layer 62formed out of Ni or the like is removed by ion beam etching at an ionincident angle of 90°. In this event, the resist layer 63 formed inregions other than the concave portions is also removed slightly (seeFIG. 6D). After that, the first mask layer 61 at the bottom of eachconcave portion is removed, for example, by reactive ion etching usingSF₆ (sulfur hexafluoride) gas (see FIG. 6E). Thus, the magneticrecording layer 5 is exposed from the bottom of each concave portion.Incidentally, on this occasion, the resist layer 63 formed in regionsother than the concave portions is removed perfectly. On the other hand,the second mask layer 62 in regions other than the concave portions isremoved partially, but a certain quantity thereof remains.

Next, the magnetic recording layer 5 exposed from the bottom of eachconcave portion is removed, for example, by reactive ion etching usingCO gas and NH₃ gas as reactive gas (see FIG. 6F). Thus, the magneticrecording layer 5 is formed with a predetermined concavo-convex pattern.Incidentally, by this reactive ion etching, the second mask layer 62 inregions other than the concave portions is removed perfectly, and thefirst mask layer 61 in regions other than the concave portions is alsoremoved partially. A certain quantity of the first mask layer 61 remainson the magnetic recording layer 5. Incidentally, by use of the reactiveion etching, each concave portion in each servo pattern region 21 wherethe pitch of the concavo-convex pattern and the width of each concaveportion are larger than those in each data track region 20 is processedto be deeper than each concave portion in the data track region 20.

Next, the first mask layer 61 remaining on the magnetic recording layer5 is removed perfectly, for example, by reactive ion etching using SF₆gas as reactive gas (see FIG. 6G). Thus, the magnetic recording layer 5having a predetermined concavo-convex pattern is formed.

Residual reactive gas is removed by dry cleaning. After that, forexample, a non-magnetic material made of SiO₂ is formed into a film by asputtering method so that the non-magnetic material is filled intoconcave portions of the concavo-convex pattern made of the magneticrecording layer 5. Thus, a non-magnetic layer 6 is formed (see FIG. 6H).The non-magnetic layer 6 is formed not only in the concave portions ofthe concavo-convex pattern but also on the magnetic recording layer 5.When the non-magnetic layer 6 is formed in many steps, the surface of ato-be-processed body filmed therewith can be flattened. For example, asecond layer of the non-magnetic layer is formed with bias power beingapplied to the surface of the to-be-processed body to be filmed with thenon-magnetic layer. Thus, the flatness of the upper surface of theformed non-magnetic layer can be improved.

Next, the surface of the to-be-processed body wholly filmed with thenon-magnetic layer 6 is etched by an ion beam etching method using Argas. Thus, the non-magnetic layer 6 higher than the surface position ofthe magnetic recording layer 5 is removed so that the surface of theto-be-processed body is flattened (see FIGS. 7A-7C). For example, theto-be-processed body filmed with the non-magnetic layer 6 on themagnetic recording layer 5 is irradiated with an ion beam 71, forexample, at an incident angle of 2°. The surface of the to-be-processedbody can be flattened thus by ion beam etching.

Incidentally, in this specification, the term “ion beam etching” is usedas a generic term of processing methods for irradiating ato-be-processed body with ionized gas to thereby remove a layer, such asion milling. The ion beam etching is not limited to a processing methodfor irradiating the to-be-processed body with a narrowed ion beam. Theterm “incident angle” means an incident angle ofan ion beam (ionizedgas) with respect to the surface of the to-be-processed body, whichangle is synonymous with the angle formed between the surface of theto-be-processed body and the central axis of the ion beam. For example,when the central axis of the ion beam is parallel to the surface of theto-be-processed body, the incident angle is 0°. When the central axis ofthe ion beam is perpendicular to the surface of the to-be-processedbody, the incident angle is 90°.

Next, the protective layer 7 is formed on the upper surfaces of themagnetic recording layer 5 and the non-magnetic layer 6 by a CVD(Chemical Vapor Deposition) method. Further the lubricating layer 8 isformed on the protective layer 7 by a dipping method. Thus, the magneticrecording medium according to the invention is completed.

In the aforementioned method for manufacturing the magnetic recordingmedium, reactive ion etching is used as a method for etching themagnetic recording layer 5 to form a predetermined concavo-convexpattern. Accordingly, each servo pattern region 21 where the pitch ofthe concavo-convex pattern and the width of each concave portion arelarger than those in each data track region 20 is etched to be deeperthan the data track region 20. As a result, when the non-magnetic layer6 is filled into concave portions of the formed concavo-convex patternby a sputtering method or the like, the surface position of thenon-magnetic layer 6 formed in the servo pattern region 21 is generallylower than the surface position of the non-magnetic layer 6 formed inthe data track region 20. Accordingly, by ion beam etching performedsubsequently, the surface position of the non-magnetic layer 6 in theservo pattern region 21 can be made lower than the surface position ofthe non-magnetic layer 6 in the data track region 20 as shown in FIGS.3A-3B and 4A-4B. Thus, concaves and convexes can be formed in the servopattern region 21.

The etching rate of the magnetic recording layer 5 or the non-magneticlayer 6 can be changed by adjusting various conditions (the gaspressure, the bias power, etc. at the time of film formation) with whichthe non-magnetic layer 6 is filled into the concave portions of theconcavo-convex pattern formed by the magnetic recording layer 5, orvarious conditions (the irradiation angle of an ion beam, the kind ofgas, etc.) with which the surface of the to-be-processed body isflattened by ion beam etching. Accordingly, in each data track region20, the etching rate of the magnetic recording layer 5 can be made equalto that of the non-magnetic layer 6. For example, when etched particlesare monitored by a mass spectroscope, it is possible to use a method inwhich flattening is completed as soon as the material of the magneticrecording layer 5 begins to be detected. By combination of theaforementioned methods, the structures shown in FIGS. 3A-3B, 4A-4B and5A-5B can be obtained.

As described above, in order to manufacture the magnetic recordingmedium according to the invention, the depth of the concave portions ofthe concavo-convex pattern can be changed between each data track region20 and each servo pattern region 21 particularly by reactive ionetching. Thus, concaves and convexes can be provided in the surface ofthe servo pattern region 21 after the non-magnetic layer is filled intothe concave portions. Further, processing conditions such as etchingrates of the magnetic recording layer 5 and the non-magnetic layer 6,ion beam incident angle dependencies or gas dependencies of the etchingrates of the layers 5 and 6, etc. are optimized so that magneticrecording media according to the aforementioned embodiments can bemanufactured. In a hard disk drive or the like provided with such amagnetic recording medium, the surface of the magnetic recording mediumis not too flat, so that increase in frictional resistance between themagnetic recording medium and a head slider can be suppressed. As aresult, increase in frictional resistance between the magnetic recordingmedium and the head slider flying on the magnetic recording medium andreading/writing magnetic recording information can be suppressed toprevent stiction between the magnetic recording medium and the headslider.

(Magnetic Recording-reproducing Device)

Next, description will be made about magnetic recording-reproducingdevice according to the invention.

FIG. 8 is a perspective view showing an embodiment of magneticrecording-reproducing device according to the invention. The magneticrecording-reproducing device 80 according to the invention has amagnetic recording medium 81 according to the invention, which has beendescribed above, a head slider 82 designed to at least partially fly onthe surface of the magnetic recording medium 81 at the time ofrecording-reproducing, and a magnetic head mounted on the head slider 82and for recording-reproducing information into/from the magneticrecording medium 81.

The magnetic recording medium 81 rotates at a high speed in accordancewith the rotation of a spindle motor 84. The head slider 82 provided onthe tip of a swing arm 83 flies due to an air flow generated by therotation of the magnetic recording medium 81. An actuator 85 is drivenin accordance with a servo signal in a servo signal region formed in themagnetic recording medium 81. Thus, the swing arm 83 is swung so thatthe head slider 82 can trace a track formed on the magnetic recordingmedium 81 accurately.

In the magnetic recording-reproducing device according to the invention,it is preferable that the circumferentially continuous length of eachdata track region 20 in the magnetic recording medium 81 does not exceedthe circumferential length of the head slider 82. With thisconfiguration, at least a part of the head slider 82 is always locatedon any one of the servo pattern regions 21 having concaves and convexes.Thus, stiction of the head slider can be prevented more surely.

As described above, the magnetic recording-reproducing device accordingto the invention has the aforementioned magnetic recording mediumaccording to the invention. Accordingly, it is possible to preventstiction between the magnetic recording medium and the head sliderflying on the magnetic recording medium and mounted with the magnetichead for reading/writing magnetic recording information. Thus, it ispossible to provide magnetic recording-reproducing device which canconspicuously suppress problems such as crush of the magnetic headcaused by the stiction and which is low in spacing loss between themagnetic head and the magnetic recording layer and excellent in costmerit.

EXAMPLES

The invention will be described below more in detail using examples andcomparative examples.

(Manufacturing of To-Be-Processed Body)

First, a to-be-processed body for forming a discrete track type magneticrecording medium was manufactured. A disk substrate 1 made of a glasssubstrate and having a thickness of 630 μm was filmed with an undercoatlayer 2, a soft magnetic layer 3, an orientation layer 4, a magneticrecording layer 5 (20 nm thick), a first mask layer (TiN: 25 nm thick)and a second mask layer (Ni: 10 nm thick) in that order. The filmedsample was coated with negative type resist (brand name: NEB22A made bySumitomo Chemical Co., Ltd.) by a spin coat method so that a resistlayer 100 nm thick was formed. By use of a stamper having apredetermined concavo-convex shape, the concavo-convex shape wastransferred to the resist layer on the sample surface by a press using anano-imprint method, and reactive ion etching using O₂ gas as reactivegas was performed thereon. Thus, a resist pattern made frommicro-figures was formed while the resist layer at the bottom of eachconcave portion was removed. Next, using the resist pattern as a mask,the micro-figures of the resist pattern were transferred to the secondmask layer by an ion beam etching method using Ar gas. Thus, a secondmask pattern made from the micro-figures was formed. Next, using thesecond mask pattern as a mask, the micro-figures of the second maskpattern were transferred to the first mask layer by a reactive ionetching method using SF₆ gas as reactive gas. Thus, a first mask patternmade from the micro-figures was formed. Next, using the first maskpattern as a mask, the micro-figures of the first mask pattern weretransferred to the magnetic recording layer 5 by a reactive ion etchingmethod using CO gas and NH₃ gas as reactive gas. Thus, a magneticrecording layer pattern made from the micro-figures was formed. Next,the first mask layer retained on the magnetic recording layer patternwas removed by a reactive ion etching method using SF₆ gas as reactivegas.

By the aforementioned method, a to-be-processed body for forming adiscrete track type magnetic recording medium was manufactured. Theprocessed dimensions of each data track region 20 are 150 nm in trackpitch, 90 nm in pattern width of the magnetic recording layer, 1:1.5 inratio (concave-convex ratio) of the area of each portion (concaveportion of the concavo-convex pattern) where the magnetic recordinglayer was not formed to the area of each portion (convex portion of theconcavo-convex pattern) where the magnetic recording layer was formed,60 nm in width of each portion (concave portion of the concavo-convexpattern) where the magnetic recording layer was not formed, and 22 nm indepth of each concave portion. The position of the magnetic recordinglayer pattern (concavo-convex pattern) was set to range radially from 10mm to 30 mm. On the other hand, as for the processed dimensions of eachservo pattern region 21, for example, in a servo burst signal region 24as shown in FIG. 9, the magnetic recording layer pattern constitutingeach convex portion 92 of the concavo-convex pattern measured 150 nm inradial width W_(L) 5 and 100-300 nm in circumferential width W_(S) 5,and the pattern constituting each concave portion 91 of theconcavo-convex pattern measured 150 nm in radial width W_(L) 6 and100-300 nm in circumferential width W_(S) 6. Further, as shown in FIG.9, the ratio (concave-convex ratio: S6:S5) of the area S6 of eachconcave portion 91 where the magnetic recording layer was not formed tothe area S5 of each convex portion 92 formed out of the magneticrecording layer was set to be 1:3. Incidentally, the depth of eachconcave portion 91 was 30 nm, and the position of the magnetic recordinglayer pattern (concavo-convex pattern) was set to range radially from 10mm to 30 mm in the same manner as in the data track region 20.

Example 1

A non-magnetic layer 6 was formed on the to-be-processed body obtainedin the aforementioned manner. First, a film of SiO₂ was formed to be 100nm thick by a sputtering method in the conditions of 500 W in filmformation power, 150 W in bias power and 0.3 Pa in Ar gas pressure.Incidentally, the film thickness here means the thickness of a film on aflat surface when the film was formed on the flat surface in parallel.Ion beam etching using Ar gas and having an incident angle of 2° wasperformed on the to-be-processed body after the non-magnetic layer 6 wasformed. Thus, a surplus of SiO_(s) on the magnetic recording layer 5 wasremoved so that the surface was flattened. The etching was monitored bya mass spectroscope. The flattening was completed as soon as themagnetic recording layer in the data track region 20 began to bedetected.

Incidentally, the surface position of the non-magnetic layer 6 is lowerin each servo pattern region 21 than in each data track region 20 whenthe non-magnetic layer 6 has been formed. Accordingly, when ion beametching is kept on, the magnetic recording layer 5 in the servo patternregion 21 begins to be detected, and after that, the magnetic recordinglayer 5 in the data track region 20 begins to be detected. Thedetections of the both can be distinguished based on a change of therate detected in mass spectrograph. Thus, the flattening of the surfaceof each data track region 20 can be attained by suspending the ion beametching as soon as the magnetic recording layer 5 in the data trackregion 20 begins to be detected.

DLC 2 nm thick was formed thereon as the protective film 7 by a CVDmethod. Further on the protective film 7, perfluoropolyether (PFPE) 2 nmthick was formed as the lubricating layer 8 by a dipping method. Thus, amagnetic recording medium in Example 1 was manufactured.

The magnetic recording medium manufactured thus had a mode in which thesurface roughness of concaves and convexes existing in the surface ofeach data track region 20 was extremely low, while the surface roughnessof concaves and convexes existing in the surface of each servo patternregion 21 was high. In this mode, of the concaves and convexes in thesurface of the servo pattern region 21, the convex portions were made ofthe magnetic recording layer, and there was a difference in surfacelevel between the magnetic recording layer and the non-magnetic layerforming the concave portions.

The irradiation angle of an ion beam was regarded as 0° in the case ofirradiation with the ion beam incident on the magnetic recording mediumin parallel to its surface, and regarded as 90° in the case ofirradiation with the ion beam incident on the magnetic recording mediumperpendicularly to its surface. In Example 1, due to irradiation withthe ion beam at an incident angle of 2°, the etching rate of thenon-magnetic layer is higher than the etching rate of the magneticrecording layer. Thus, the etching depth of the non-magnetic layerfilled between elements of the magnetic recording layer in each servopattern region 21 becomes larger.

The difference in surface level between each concave and each convex ineach servo pattern region 21 of the magnetic recording mediummanufactured thus was 2.5 nm, and Ra (arithmetical mean deviation of theassessed profile) thereof was 0.9 nm. On the other hand, Ra(arithmetical mean deviation of the assessed profile) in the surface ofeach data track region 20 was 0.3 nm.

FIG. 10 shows the relationship between the arithmetical mean deviationof the assessed profile and the frictional coefficient in the surface ofthe magnetic recording medium, obtained from a sliding test of a headslider. The relationship between the arithmetical mean deviation of theassessed profile and the frictional coefficient shown in FIG. 10 wasobtained using samples different in arithmetical mean deviation of theassessed profile and measured by a tester to be used in a CSS (ContactStart Stop) test. As is apparent from the relationship in FIG. 10, thefrictional coefficient rises suddenly when the arithmetical meandeviation of the assessed profile of the surface is not higher than 0.3nm. This fact indicates that stiction of the magnetic head occurs easilywhen the arithmetical mean deviation of the assessed profile of thesurface is not higher than 0.3 nm.

Example 2

A magnetic recording medium shown in FIGS. 4A-4B was manufactured in amethod similar to that in Example 1. This magnetic recording mediumcould be manufactured as follows. That is, in the ion beam etching ofthe non-magnetic layer in Example 1, the ion beam etching had beensuspended since the magnetic recording layer 5 in each servo patternregion 21 began to be detected and till the magnetic recording layer 5in each data track region 20 began to be detected. Thus, flattening wascompleted.

Example 3

A magnetic recording medium shown in FIGS. 5A-5B was manufactured in amethod similar to that in Example 1. This magnetic recording mediumcould be manufactured as follows. That is, in the ion beam etching ofthe non-magnetic layer in Example 1, the ion beam etching was oncesuspended as soon as the magnetic recording layer 5 in each servopattern region 21 began to be detected. The incident angle was changedfrom 2° to 90° (90° was an incident angle with which “the etching rateof the magnetic recording layer 5 was higher than the etching rate ofthe non-magnetic material (SiO₂)”), and the ion beam etching wasresumed. The ion beam etching was suspended as soon as the magneticrecording layer 5 in each data track region 20 began to be detected.Thus, flattening was completed.

This application is based upon and claims the benefit of priority ofJapanese Patent Application No. 2004-50816 filed on Feb. 26, 2004, thecontents of which are incorporated herein by reference in its entirety.

1. A magnetic recording medium comprising: a disk substrate; a magneticrecording layer formed with a predetermined concavo-convex pattern onsaid disk substrate; and a non-magnetic layer filled into concaveportions of said concavo-convex pattern, wherein said magnetic recordingmedium has data track regions and servo pattern regions, whereinconcaves and convexes exist in a surface of each of said servo patternregions, and wherein arithmetical mean deviation of the assessed profileof a surface of each of said data track regions is lower thanarithmetical mean deviation of the assessed profile of a surface of eachof said servo pattern regions.
 2. A magnetic recording medium accordingto claim 1, wherein arithmetical mean deviation of the assessed profileof a surface of each of said servo pattern regions is not lower than 0.3nm.
 3. A magnetic recording medium according to claim 1, wherein adifference in surface level between each of said concaves and each ofsaid convexes existing in a surface of each of said servo patternregions is not higher than 6 nm.
 4. A magnetic recording mediumaccording to claim 1, wherein said concaves and convexes existing in asurface of each of said servo pattern regions are formed by a differencein surface level between said magnetic recording layer and saidnon-magnetic layer, and a thickness-direction surface position of saidmagnetic recording layer is higher than a thickness-direction surfaceposition of said non-magnetic layer in each of said servo patternregions.
 5. A magnetic recording medium according to claim 1, wherein athickness-direction surface position of said non-magnetic layer is nothigher than a thickness-direction surface position of said magneticrecording layer.
 6. A magnetic recording medium according to claim 1,wherein said magnetic recording layer is absent from said concaveportions of said concavo-convex pattern.
 7. A magnetic recording mediumaccording to claim 1, wherein a non-magnetic material for forming saidnon-magnetic layer is comprised of one or more compounds selected fromoxides, nitrides and carbides.
 8. A magnetic recording medium accordingto claim 1, wherein a non-magnetic material for forming saidnon-magnetic layer is a material having an amorphous structure or amicrocrystalline material.
 9. A magnetic recording medium according toclaim 1, wherein a non-magnetic material for forming said non-magneticlayer has silicon dioxide as a main component thereof.
 10. Magneticrecording-reproducing device comprising: a magnetic recording mediumaccording to claim 1; a head slider designed to at least partially flyon a surface of said magnetic recording medium at the time ofrecording-reproducing; and a magnetic head mounted on said head sliderand for recording-reproducing information into/from said magneticrecording medium.
 11. Magnetic recording-reproducing device according toclaim 10, wherein circumferentially continuous length of each of saiddata track regions in said magnetic recording medium is not longer thancircumferential length of said head slider.